#include<stdio.h>
int  Strlen(char * arr) {
	int count = 0;
	while ( * arr != '\0') {
		count++;
		arr++;
	}
	return count;
}
void Invert(char * arr, int n) {
	int right = 0;
	int left = n - 1 ;
	while (right < left) {
		char temp = arr[right];
		arr[right] = arr[left];
		arr[left] = temp;
		right++;
		left--;
	}
}
int main () {
	char arr[] = "abcdef";
	int n = Strlen(arr);
	Invert(arr, n);
	for (int i = 0; i < n; i++) {
		printf("%c ", arr[i]);
	}
	return 0;
}
